This invention relates to a backshelf compensating exhaust hood apparatus and particularly to such a hood apparatus adapted to be mounted adjacent commercial cooking equipment or to other industrial, institutional or commercial devices generating fumes, particles and the like to be exhausted therefrom.
Cooking equipment in restaurants and other institutional kitchens generate fumes which are desirably exhausted from above the appliance to the exterior of the room and/or building. This is particularly true of gas fired grills, griddles, deep-fat fryers and the like. In practically all commercial kitchens, as well as various industrial and institutional work areas, an exhaust hood is mounted in overlying relationship to the work area and is operable to draw the contaminated environment from the work area and discharge the contaminated environment to the exterior of the enclosure. Various types of wall and appliance mounted exhaust hoods have been developed. A particularly satisfactory compensating exhaust unit which has been commercially developed is disclosed in U.S. Pat. No. 4,153,044 which issued Aug. 8, 1979 to Louis A. Nett and which is assigned to a common assignee with the present invention. The exhaust hood disclosed in such patent is typically identified as a backshelf type of exhaust apparatus. The unit is adapted to be mounted on a wall or directly to the cooking equipment, with a back wall which projects upwardly above the cooking area. An exhaust chamber is located to the back side of the appliance and includes a filter through which the exhaust from the equipment is passed to remove grease and other types of objectionable foreign matter prior to discharge to the room exterior. The filter is inclined forwardly over the cooking equipment. The backshelf exhaust hood of the patent provides a low profile induction unit, with induction air supplied through a special passageway in the upper wall portion of the exhaust hood. The backshelf exhaust hood is generally defined by a top wall and partially enclosing vertical side wall which generally includes the back wall and opposite side walls, all of which may be supported off the floor by a plurality of support legs, or attached to a wall for support. Injected air under pressure is directed through a supply duct and the top wall to form an induction air stream which passes across the exhaust hood into the filter. An exhaust duct is mounted behind the supply duct and leads from the exhaust chamber to the exhaust fan. Air, preferably, from outside the building, is drawn in by an intake fan and forced under pressure through the supply duct and the top wall of the hood enclosure, as more fully developed in the above patent. Interior walls within the enclosure define an air supply channel or passageway which directs the incoming induction air to the front of the top wall. A deflector panel mounted at the front of the top wall portion redirects the flowing air backwardly and downwardly at an angle toward the exhaust passageway in the back of the apparatus, such that the downwardly flowing air strikes the filter at substantially a right angle. The high velocity stream of induction air provides an area of lower than ambient pressure and draws vapor arising from the cooking surface upwardly into the filter and thereby assists the function of the exhaust fan. As more fully disclosed in said patent, the air supply passageway in the upper wall portion is specially constructed to produce a smooth flow of air from the hood into the exhaust chamber with the air stream directed rearwardly and downwardly at an angle to engage the upper end of the filter. The filter is specially angularly oriented rearwardly with the lower end located outwardly of the upper end and is oriented such that the downwardly directed stream engages the filter substantially at right angles in the upper portion.
Provision is also made for separate exhaust of combustion gases from gas fired equipment. An exhaust duct in the hood is located to be spaced from the exhaust flue of the equipment, and includes an adjustable baffle for adapting to different equipment. Separate exhaust of combustion gases is desirable, since the expansion of the combustion gases and intermixed air would substantially increase the required exhaust volume flow rate if these gases were exhausted through the primary exhaust chamber. The hot combustion gases also tend to heat up a grease filter when passing therethrough which degrades the ability of the filter to congeal grease onto the filter from the exhaust fumes.
Although the induction hood such as shown in the above patent has found wide commercial acceptance, conditions have arisen wherein optimum exhausting from a cooking range has not been obtained with present day backshelf hood devices.